[Inference API] Add API to get configuration of inference services (#114862)

* Adding API to get list of service configurations

* Update docs/changelog/114862.yaml

* Fixing some configurations

* PR feedback -> Stream.of

* PR feedback -> singleton

* Renaming ServiceConfiguration to SettingsConfiguration. Adding TaskSettingsConfiguration

* Adding task type settings configuration to response

* PR feedback

Author: ymao1

docs/changelog/114862.yaml

@@ -0,0 +1,5 @@
+pr: 114862
+summary: "[Inference API] Add API to get configuration of inference services"
+area: Machine Learning
+type: enhancement
+issues: []

server/src/main/java/module-info.java

@@ -469,5 +469,6 @@
             org.elasticsearch.serverless.shardhealth,
             org.elasticsearch.serverless.apifiltering;
     exports org.elasticsearch.lucene.spatial;
+    exports org.elasticsearch.inference.configuration;
 
 }

server/src/main/java/org/elasticsearch/inference/EmptySettingsConfiguration.java

@@ -0,0 +1,19 @@
+/*
+ * Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
+ * or more contributor license agreements. Licensed under the "Elastic License
+ * 2.0", the "GNU Affero General Public License v3.0 only", and the "Server Side
+ * Public License v 1"; you may not use this file except in compliance with, at
+ * your election, the "Elastic License 2.0", the "GNU Affero General Public
+ * License v3.0 only", or the "Server Side Public License, v 1".
+ */
+
+package org.elasticsearch.inference;
+
+import java.util.Collections;
+import java.util.Map;
+
+public class EmptySettingsConfiguration {
+    public static Map<String, SettingsConfiguration> get() {
+        return Collections.emptyMap();
+    }
+}

server/src/main/java/org/elasticsearch/inference/InferenceService.java

@@ -16,6 +16,7 @@
 import org.elasticsearch.core.TimeValue;
 
 import java.io.Closeable;
+import java.util.EnumSet;
 import java.util.List;
 import java.util.Map;
 import java.util.Set;
@@ -71,6 +72,14 @@ default void init(Client client) {}
      */
     Model parsePersistedConfig(String modelId, TaskType taskType, Map<String, Object> config);
 
+    InferenceServiceConfiguration getConfiguration();
+
+    /**
+     * The task types supported by the service
+     * @return Set of supported.
+     */
+    EnumSet<TaskType> supportedTaskTypes();
+
     /**
      * Perform inference on the model.
      *

server/src/main/java/org/elasticsearch/inference/InferenceServiceConfiguration.java

@@ -0,0 +1,183 @@
+/*
+ * Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
+ * or more contributor license agreements. Licensed under the "Elastic License
+ * 2.0", the "GNU Affero General Public License v3.0 only", and the "Server Side
+ * Public License v 1"; you may not use this file except in compliance with, at
+ * your election, the "Elastic License 2.0", the "GNU Affero General Public
+ * License v3.0 only", or the "Server Side Public License, v 1".
+ */
+
+package org.elasticsearch.inference;
+
+import org.elasticsearch.ElasticsearchParseException;
+import org.elasticsearch.common.bytes.BytesReference;
+import org.elasticsearch.common.io.stream.StreamInput;
+import org.elasticsearch.common.io.stream.StreamOutput;
+import org.elasticsearch.common.io.stream.Writeable;
+import org.elasticsearch.common.xcontent.XContentHelper;
+import org.elasticsearch.xcontent.ConstructingObjectParser;
+import org.elasticsearch.xcontent.ParseField;
+import org.elasticsearch.xcontent.ToXContentObject;
+import org.elasticsearch.xcontent.XContentBuilder;
+import org.elasticsearch.xcontent.XContentParser;
+import org.elasticsearch.xcontent.XContentParserConfiguration;
+import org.elasticsearch.xcontent.XContentType;
+
+import java.io.IOException;
+import java.util.ArrayList;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+import java.util.Objects;
+
+import static org.elasticsearch.xcontent.ConstructingObjectParser.constructorArg;
+
+/**
+ * Represents the configuration field settings for an inference provider.
+ */
+public class InferenceServiceConfiguration implements Writeable, ToXContentObject {
+
+    private final String provider;
+    private final List<TaskSettingsConfiguration> taskTypes;
+    private final Map<String, SettingsConfiguration> configuration;
+
+    /**
+     * Constructs a new {@link InferenceServiceConfiguration} instance with specified properties.
+     *
+     * @param provider       The name of the service provider.
+     * @param taskTypes      A list of {@link TaskSettingsConfiguration} supported by the service provider.
+     * @param configuration  The configuration of the service provider, defined by {@link SettingsConfiguration}.
+     */
+    private InferenceServiceConfiguration(
+        String provider,
+        List<TaskSettingsConfiguration> taskTypes,
+        Map<String, SettingsConfiguration> configuration
+    ) {
+        this.provider = provider;
+        this.taskTypes = taskTypes;
+        this.configuration = configuration;
+    }
+
+    public InferenceServiceConfiguration(StreamInput in) throws IOException {
+        this.provider = in.readString();
+        this.taskTypes = in.readCollectionAsList(TaskSettingsConfiguration::new);
+        this.configuration = in.readMap(SettingsConfiguration::new);
+    }
+
+    static final ParseField PROVIDER_FIELD = new ParseField("provider");
+    static final ParseField TASK_TYPES_FIELD = new ParseField("task_types");
+    static final ParseField CONFIGURATION_FIELD = new ParseField("configuration");
+
+    @SuppressWarnings("unchecked")
+    private static final ConstructingObjectParser<InferenceServiceConfiguration, Void> PARSER = new ConstructingObjectParser<>(
+        "inference_service_configuration",
+        true,
+        args -> {
+            List<String> taskTypes = (ArrayList<String>) args[1];
+            return new InferenceServiceConfiguration.Builder().setProvider((String) args[0])
+                .setTaskTypes((List<TaskSettingsConfiguration>) args[1])
+                .setConfiguration((Map<String, SettingsConfiguration>) args[2])
+                .build();
+        }
+    );
+
+    static {
+        PARSER.declareString(constructorArg(), PROVIDER_FIELD);
+        PARSER.declareObjectArray(constructorArg(), (p, c) -> TaskSettingsConfiguration.fromXContent(p), TASK_TYPES_FIELD);
+        PARSER.declareObject(constructorArg(), (p, c) -> p.map(), CONFIGURATION_FIELD);
+    }
+
+    public String getProvider() {
+        return provider;
+    }
+
+    public List<TaskSettingsConfiguration> getTaskTypes() {
+        return taskTypes;
+    }
+
+    public Map<String, SettingsConfiguration> getConfiguration() {
+        return configuration;
+    }
+
+    @Override
+    public XContentBuilder toXContent(XContentBuilder builder, Params params) throws IOException {
+        builder.startObject();
+        {
+            builder.field(PROVIDER_FIELD.getPreferredName(), provider);
+            builder.field(TASK_TYPES_FIELD.getPreferredName(), taskTypes);
+            builder.field(CONFIGURATION_FIELD.getPreferredName(), configuration);
+        }
+        builder.endObject();
+        return builder;
+    }
+
+    public static InferenceServiceConfiguration fromXContent(XContentParser parser) throws IOException {
+        return PARSER.parse(parser, null);
+    }
+
+    public static InferenceServiceConfiguration fromXContentBytes(BytesReference source, XContentType xContentType) {
+        try (XContentParser parser = XContentHelper.createParser(XContentParserConfiguration.EMPTY, source, xContentType)) {
+            return InferenceServiceConfiguration.fromXContent(parser);
+        } catch (IOException e) {
+            throw new ElasticsearchParseException("failed to parse inference service configuration", e);
+        }
+    }
+
+    @Override
+    public void writeTo(StreamOutput out) throws IOException {
+        out.writeString(provider);
+        out.writeCollection(taskTypes);
+        out.writeMapValues(configuration);
+    }
+
+    public Map<String, Object> toMap() {
+        Map<String, Object> map = new HashMap<>();
+
+        map.put(PROVIDER_FIELD.getPreferredName(), provider);
+        map.put(TASK_TYPES_FIELD.getPreferredName(), taskTypes);
+        map.put(CONFIGURATION_FIELD.getPreferredName(), configuration);
+
+        return map;
+    }
+
+    @Override
+    public boolean equals(Object o) {
+        if (this == o) return true;
+        if (o == null || getClass() != o.getClass()) return false;
+        InferenceServiceConfiguration that = (InferenceServiceConfiguration) o;
+        return provider.equals(that.provider)
+            && Objects.equals(taskTypes, that.taskTypes)
+            && Objects.equals(configuration, that.configuration);
+    }
+
+    @Override
+    public int hashCode() {
+        return Objects.hash(provider, taskTypes, configuration);
+    }
+
+    public static class Builder {
+
+        private String provider;
+        private List<TaskSettingsConfiguration> taskTypes;
+        private Map<String, SettingsConfiguration> configuration;
+
+        public Builder setProvider(String provider) {
+            this.provider = provider;
+            return this;
+        }
+
+        public Builder setTaskTypes(List<TaskSettingsConfiguration> taskTypes) {
+            this.taskTypes = taskTypes;
+            return this;
+        }
+
+        public Builder setConfiguration(Map<String, SettingsConfiguration> configuration) {
+            this.configuration = configuration;
+            return this;
+        }
+
+        public InferenceServiceConfiguration build() {
+            return new InferenceServiceConfiguration(provider, taskTypes, configuration);
+        }
+    }
+}